The objectives of this contract would be to develop, test, and evaluate a number of different devices and techniques which are designed to measure lung volumes, mechanical properties of the lung, transcutaneous blood gases, and regional ventilation in neonates and young children. The proposal is composed of six projects. The first project is to complete the development of an ultrasonic transducer used to measure helium gas concentrations. The helium gas analyzer will be applied to the determination of anatomic dead space and FRC. A second project involves the design of suitable face mask for use in testing children. Flow properties and patient acceptance of these pieces of equipment will be tested and evaluated.